getpart.pm: Fix a comment typo
runtests.pl: Don't expect $TESTDIR/DISABLED to exist

If a non-standard $TESTDIR is used the file may not be necessary.

Previously a "missing" file resulted in the warning:
readline() on closed filehandle D at ./runtests.pl line 4940.
runtests.pl: Remove filteroff() which hasn't been used since 2001
tests: Fix a couple of incomplete response lines